The invention concerns a method and apparatus for controlling reeling used in connection with the making of paper/board/an equivalent web-like material, in which reeling a reeler is used, which comprises a reeling element, a reeling core, around which the web is reeled to form a reel, as well as elements for loading the reeling core and the reeling element against each other in order to bring about a reeling nip in between the reeling element and the reel.
The invention relates generally to the making of paper, tissue or board or some other equivalent web-like product and to the associated reeling. When referring hereinafter to a papermaking machine or to paper, such reference also includes a machine intended for making the above-mentioned products or the product to be made by it.
The finished paper web of a papermaking machine or other device processing a web-like product is reeled around a roll in a reeler located at the end of the machine, which is called a reeling drum. The reel formed around the roll from the paper web of full width emerging from the machine is called a machine reel. In the reeling device, that is, in the reeler, a reeling cylinder rotates at a peripheral speed equal to the speed of the paper web. The reeling cylinder is bearing-mounted in the body of the reeling device with the aid of shafts located at its ends. At its one end the reeling cylinder is connected to a driving device, which for its part is in connection with the overall drive of the machine in such a way that the reeling cylinder's peripheral speed is equal to the speed of the completed paper web emerging from the machine. This type of reeler goes under the name of Pope reeler. Besides the reeling cylinder, a reeling belt may also be used in the reeler, which belt is known from the patent FI-94231 of Metso Paper, Inc.
The finished web is collected on a reeling drum located at the reeling station, while the drum is loaded at the same time towards the reeling cylinder. The reeling drum may have its motional power with the aid of friction through the paper web from the reeling cylinder (a so-called peripherally driven Pope reeler) or according to a solution in general use today, it can be provided with a drive, whereby the reeler is called a center-driven reeler.
When a sufficient quantity of paper web has accumulated on the reeling drum, the reel is dismounted from the surface of the reeling cylinder. The reel's peripheral speed will decrease as the reel is slowed down, and a bag will form in the web before the reeling drum, which bag is guided with the aid of an airflow and placed around a new empty reeling drum brought to the reeling cylinder. The paper web moving on to a full reeling drum will break off immediately and it starts winding around the new reeling drum. Other alternative ways are also used, and they depend on the basis weight of the paper, among other things.
In connection with the reeling, especially with today's high and constantly increasing speeds, an over-pressure occurs in the inlet jaw between the web and the reeling cylinder, in consequence of which an excessive quantity of air will penetrate in an undesirable manner between the reeling cylinder and the arriving paper web. This problem occurs especially in broad machines operating at high speeds and it is especially harmful with paper grades poorly permeable to air (with grades calendered on line in particular).
The forming air bag, which is located just before the reeling nip between the reeling cylinder and the reel, makes air penetrate between the paper layers, whereby smaller air bags will form especially between the topmost layers. The phenomenon is illustrated in the appended FIG. 1B, which shows air bags b forming in the reel in spaces between the topmost paper layers P1, P2, P3, P4. The air can only escape from the ends of the reel, whereby air will collect in the reel's middle parts in particular. This causes several various problems, such as folding, looseness in the reel structure and various flaws in the paper quality. The phenomenon can occur, for example, as a star pattern visible at the end of the reel. The quality problems resulting in this manner will for their part give rise to an increasing quantity of rejects in the production.
An attempt to solve the airbag problem is made, for example, by a solution presented in the printed patent specification FI 107327, wherein the reeling cylinder is grooved to conduct the air away in a controlled manner from the reeling nip.
Another problem occurring in connection with reeling relates to cross-cutting of the paper web in connection with the reel change. Irrespective of the cross-cutting method used, the problem in connection with cross-cutting is the occurrence of loose pieces of paper, that is, fodder, and their ending up inside the material to be reeled. If in connection with unreeling fodder drifts to the following process stage, typically in connection with the calendering on to rolls, then damages may result, which must be corrected at high costs. The calenderer's roll coatings in particular are easily damaged by the impact of superfluous particles.
According to the state of the art, attempts have been made to solve said fodder problem by leaving a sufficient quantity unused of the reel's final part in connection with the unreeling. The idea is to make sure in this manner that no fodder will occur in the part of the reel intended for use. However, the consequence is a loss of material, since an unnecessarily large quantity of paper is often rejected just to be sure.
Of the problematic situations occurring with the reeler such a situation may also be mentioned, where at least a double folding has formed in the edge of the paper web or equivalent and such a double part begins assembling in the reel. As the reel is growing, the nip will draw in this double area only, but not in the other part of the reel. The occurrence of a double edge may be caused, for example, by flapping of the edge, which may result from a too high running speed, profile problems in the web, breaking of the edge or quality flaws occurring in connection with the calendering, such as a sharp fold in the paper.
As the size of the roll is growing, a double edge will cause mechanical tensions in the reel. The mechanical tension is released when the paper layers in the reel yield, and in this way a situation arises where the reel disintegrates. Disintegration may even take place explosively, whereby pieces weighing 0.5-5 kilos may hurl out of the disintegrating reel into the environment. The hurling reel pieces cause a hazardous situation for people nearby. They may also cause mechanical damage to equipment nearby.
Furthermore, such a problematic situation occurs in connection with reeling, where the paper web piles up or folds up on the reel bottom in connection with the reel change, and a situation where the web does not move on to the reel but drifts around the reeling cylinder or elsewhere near the reeler. In addition, the web may have split up in the machine direction before the reeling, and this will lead to quality problems in the reeling. At times when the edges of a split web have overlapped, the split web is not necessarily detected by the state-of-the-art devices observing holes occurring in the web.